1. Field of the Invention
This invention relates to a structure of a floor slab bridge in a bridge built up in a river or on land, and more particularly to a structure of a floor slab bridge in which a columnar H-shaped steel is used as a main girder material.
2. Related Art
A floor slab bridge is disclosed by Japanese Patent Application Laid-Open Publication No. H09-221717 as typically illustrated in its FIGS. 1 and 2, in which steel sheet piles 11 are used as a bottom plate, T-shaped steels or H-shaped steels (main girder member 13) are welded to the steel sheet piles 11 such that the T-shaped steels or H-shaped steels are spacedly arranged thereon. Adjacent steel sheet piles 11 are joined by pawls 12 disposed at left and right side end faces of each steel sheet pile 11. Concrete is placed in a space between an upper flange of each T-shaped steel or H-shaped steel and the steel sheet pile 11 through a concrete inlet port which is formed between the upper flanges of each T-shaped steel or H-shaped steel so that a lower concrete layer is formed, and concrete is placed on the upper flange so that an upper concrete layer is formed, wherein the upper concrete layer is to be joined with the lower concrete layer through the concrete inlet port.
Similarly, FIG. 5 of the above publication shows a floor slab bridge in which a plurality of T-shaped steels or H-shaped steels are arranged in side-by-side relation on a bottom plate 3 composed of a single steel plate and concrete is placed thereon.
In those floor slab bridges, a side plate 16 is applied to the outer side surface of the side concrete layer placed on the outer side surface of the leftmost or rightmost T-shaped steel or H-shaped steel, and in the floor slab bridge shown in FIGS. 1 and 2, a PC steel material 18 is pierced through a web plate formed of T-shaped steel or H-shaped steel, which are arranged in a side-by-side relation, a lower concrete layer and a block which is called a cross girder 19, from the outer side surface of the side plate 16. Both ends of the PC steel material 18 are fastened at the outer side surfaces of the side plates 16, and play at the joint part of the pawl 12 is set to a maximum, thereby applying a pre-stress to the concrete layer. Necessarily, the PC steel material 18 used as this pre-stress means is left in its exposed state at the fastening parts on both ends at the outer side surfaces of the side plates 16.
In the above-mentioned conventional structure(s), the bottom plate is formed by the steel sheet piles 11, and the T-shaped steels or H-shaped steels are spacedly arranged in side-by-side relation on the bottom plate as in the manner mentioned above. Play at the joint part of the pawl 12 of the steel sheet pile 11 is set to a maximum. After the concrete is cured, the PC steel material 18 is fastened at the outer side surfaces of the side plates 16, thereby applying a pre-stress to the concrete layer. The PC steel material 18 pierces through the cross girder 19, with play, thus enabling a fastening which can apply the pre-stress. Accordingly, the PC steel material 18 is not joined with the concrete at all. This means that the PC steel material 18 does not function as a concrete reinforcement.
Therefore, if a vertical load (live load) attributable to a passage of vehicles, etc. is applied to the floor slab bridge, a shearing force would act on the concrete layer which would induce cracking of the concrete layer.
Moreover, since the PC steel material 18 is fastened at the outer side surfaces of the two side plates 16, the load is totally applied to the fastening parts of the side plates 16, thus resulting in a collapsing and/or twisting of the side plates 16.
In addition, since the fastening parts are exposed from the side plates 16, i.e., from the concrete layer, the fastening parts become rotten due to wind, rain or the like so as to degrade their original function and to spoil the outer appearance of the floor slab bridge.
Moreover, it is very troublesome to fillet weld each and every T-shaped steel or H-shaped steel over its entire length to the bottom plate 3 and the steel sheet piles 11 at constant intervals. Thus, the labor time is increased and the cost is increased, too.
The present invention has been accomplished in view of the above problems.